I. Field
The subject technology relates generally to communications systems and methods, and more particularly to systems and methods that adjust packet data content based on network conditions in a forward link only wireless network.
II. Background
Forward Link Only (FLO) is a digital wireless technology that has been developed by an industry-led group of wireless equipment and service providers. The FLO technology was designed in one case for a mobile multimedia environment and exhibits performance characteristics suited for use on cellular handsets. It uses advances in coding and interleaving to achieve high-quality reception, both real-time content streaming and other data services. FLO technology can provide robust mobile performance and high capacity without compromising power consumption. The technology also reduces the network cost of delivering multimedia content by dramatically decreasing the number of transmitters needed to be deployed. In addition, FLO technology-based multimedia multicasting complements wireless operators' cellular network data and voice services, delivering content to the same cellular handsets used on 3G networks, for example.
The FLO wireless system has been designed to broadcast real time audio and video signals, apart from non-real time services to mobile users. The respective FLO transmission is carried out using tall and high power transmitters to ensure wide coverage in a given geographical area. Further, it is common to deploy 3-4 transmitters in most markets to ensure that the FLO signal reaches a significant portion of the population in a given market. During the acquisition process of a FLO data packet several determinations and computations are made to determine such aspects as frequency offsets for the respective wireless receiver. Given the nature of FLO broadcasts that support multimedia data acquisitions, efficient processing of such data and associated overhead information is paramount. For instance, when determining frequency offsets or other parameters, complex processing and determinations are required where determinations of phase and associated angles are employed to facilitate the FLO transmission and reception of data.
Wireless communication systems such as FLO are designed to work in a mobile environment where the channel characteristics in terms of the number of channel taps with significant energy, path gains and the path delays are expected to vary quite significantly over a period of time. In an Orthogonal Frequency Division Multiplexing (OFDM) system in which FLO technology is related, a timing synchronization block in the receiver responds to changes in the channel profile by selecting the OFDM symbol boundary appropriately to maximize the energy captured in the FFT window. When such timing corrections take place, it is important that the channel estimation algorithm takes the timing corrections into account while computing the channel estimate to be used for demodulating a given OFDM symbol.
In addition to timing considerations, noise and transmission quality issues have to be accounted for in a given wireless network. In a single frequency network (SFN) such as can be provided by a FLO system, there are multiple SFNs in general. Particularly, there are both local area SFNs and wide area SFNs, where transmitters in the network are connected by multiple communication links. The data for a given SFN is generally desired to be the same, however in the presence of errors in the communications links that connect the transmitters these errors can contaminate the SFN. Similarly, if content is blacked out in one SFN, but active in another there can be destructive interference to a non-blacked out area, if the blacked out area radiates random or differently encrypted data in the blacked content's place.